Fluorescence bronchoscopy with a ratio fluorometer probe was used to
examine patients with known or suspected bronchogenic carcinoma to determine if
early lung cancer can be detected with low dose Photofrin II without skin
photosensitivity. Seventeen patients were examined 24 hours after injection of
0.25 mg/kg Photofrin II. Using a red-green (R/G) ratio of greater than 1.5 times
the mean value of normal areas as being potentially significant, both carcinoma
in situ and invasive cancers were accurately localized (sensitivity 100%,
specificity 61%). The majority of the false positive fluorescence (80%) came
from the lesions with dysplasia. The elevated R/G ratios from the cancerous and
pre-cancerous lesions were found to be due to a significantly lower green
autofluorescence. No skin photosensitivity was observed on all seventeen
patients. Ratio fluorometry was also carried out in thirty-one patients with
known or suspected lung cancer without Photofrin II. A similar diagnostic
accuracy was found (sensitivity 90%, specificity 86%). Our results suggest that
early lung cancer may be detectable by ratio fluorometry by exploiting
autofluorescence differences between tumor and normal tissues.